Symptoms of Hypophosphatemia
Severe hypophosphatemia causes reversible myocardial dysfunction, acute respiratory failure with prolonged weaning from mechanical ventilation, skeletal muscle weakness, altered mental status or coma, rhabdomyolysis, and cardiac arrhythmias, while mild to moderate hypophosphatemia is often asymptomatic. 1, 2
Acute Severe Hypophosphatemia (Serum Phosphate <1.0 mg/dL)
The most critical symptoms occur with severe phosphate depletion and include:
- Respiratory failure with difficulty weaning from mechanical ventilation due to respiratory muscle weakness 1
- Cardiac dysfunction including reversible myocardial depression and cardiac arrhythmias 1, 2
- Neurological symptoms ranging from altered mental status to coma 3, 2
- Skeletal muscle weakness progressing to rhabdomyolysis in severe cases 3, 2
- Hemolysis due to erythrocyte dysfunction 2, 4
Moderate Hypophosphatemia (1.0-2.5 mg/dL)
Most patients with moderate hypophosphatemia are asymptomatic, though symptoms may develop depending on the rate of decline and underlying phosphate stores. 3
Chronic Hypophosphatemia
In chronic renal phosphate-wasting disorders, the presentation differs:
- In children: Abnormal growth, rickets, and bone deformities including bowed legs (genu varum) or windswept deformities 1, 5
- In adults: Osteomalacia with bone pain and increased fracture risk 1, 5
Drug-Induced Hypophosphatemia (Ferric Carboxymaltose)
The symptoms of acute hypophosphatemia from ferric carboxymaltose mirror those of iron deficiency itself—worsening fatigue, myalgias, and bone pain following infusion. 1
- Patients should seek immediate medical care if experiencing worsening fatigue with muscle pain or bone pain after IV iron infusion 1
- Any patient reporting bone pain should undergo imaging to evaluate for osteomalacia or fractures 1
- Mild and moderate hypophosphatemia from IV iron can be asymptomatic and self-limiting in most patients 1
Context-Dependent Severity
The clinical effects are much more pronounced when severe hypophosphatemia occurs in high-risk settings including refeeding syndrome, chronic alcoholism, diabetic ketoacidosis, malnutrition, post-surgical states (especially after partial hepatectomy), and intensive care unit patients. 5, 4
The association with prolonged hospitalization and negative impact on patient outcomes makes recognition particularly important in critically ill patients. 1